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NEW YORK (Reuters Health) – Measuring both the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) when an inflammatory condition is suspected is not helpful and is possibly confusing, a French team reports. They recommend giving priority to CRP.

Dr. Benjamin Wyplosz at Hôpital Paul Brousse, Villejuif, investigated the concordance between ESR and CPR measured on the same day in 5777 hospitalized patients

“Agreement between ESR and CRP was observed in 67% of patients (37% of patients had normal results for both and 30% had elevated markers for both). There were some discordant results — 28% of patients had increased ESR and normal CRP, and 5% of patients had normal ESR and elevated CRP,” the team reports in The American Journal of Medicine for September.

To look into the reasons for the discrepancies, the researchers reviewed the charts of 99 randomly selected patients whose readings disagreed.

They could find no indication of an active inflammatory disorder in 68 of the 74 patients with an elevated ESR and normal CRP, so these were classified as false-positive ESR. The other six patients did have an active inflammatory disorder, and therefore had a false-negative CRP.

On the other hand, the 25 patients with a normal ESR and increased CRP all had an infection of systemic inflammation, so these cases all represented false-negative ESR results.

Dr. Wyplosz and colleagues conclude that ESR testing often gives spurious results in the hospital setting, and that CRP measurement is preferable. “Concomitant measures of ESR and CRP should be avoided,” they advise. “Assessment of discordant results may incur substantial costs and could even place patients at risk for invasive procedures.”